Integrity and reliability of the grounding grid are necessary to ensure the safe operation of the circuit system. Conductors constituting the grounding grid are buried under ground and are often broken due to poor welding and lack of welding under construction, soil erosion and other factors, thus causing degradation of the grounding discharge performance of the grounding grid, which is not only a threat to the equipment and personal safety, but also can bring huge economic losses and social impacts.
At present, the prior fault diagnostic techniques for the grounding grid are mainly based on the circuit theory, field-circuit method, nondestructive testing method and electrochemical method, but these methods either rely on design and construction drawings of the grounding grid or requires substation outage, and thus it is a technical problem to be urgently addressed during fully economic production in the electric power system to seek a novel diagnostic method and an apparatus independent of design information of the grounding grid and being capable of implementing non-excavation diagnosis without outage.